Not like the US didn't try. California spent 15yrs trying to build a high speed train and failed. Canada has been talking about building trains forever too and it usually goes nowhere because the budgets explode like every major infrastructure project these days.

UK spent $100M just to deal with bats in a single train tunnel, which is representative of the issue https://www.bbc.com/news/articles/c9wryxyljglo

Those are two unusually competent countries when it comes to trains. Try Germany or the UK for a more average outcome.

OTOH, on my visits to Europe I am simultaneously impressed with the prevalence of passenger train options, but disheartened by the price. If Europe struggles to provide really affordable trains, there isn't much hope for the US. Aside from regional train options in the densest areas, we just have too much distance to cover. Infrastructure costs would kill the plan. At this point maybe we should just be trying harder to produce renewable fuels for planes.